In many computer systems, and especially in small remote attached devices, internal instructions are read from storage in a sequence to control the operation of the processor. In the prior art, many of these remote devices contained only read-only storage (ROS) where the processor instructions were unalterably stored at the time of manufacture. When the instructions were read from the storage by the processor, a parity checker would determine if the instruction had good parity (contained the correct number of ones). If the parity was bad, these systems normally stopped the processor and set an indicator informing the operator of the device failure.
However, in many newer systems, various and different programs, sometimes large and complex, are executed in the remote devices, such as display workstations, allowing many different functions to be performed by the devices. Typically, the instructions for the remote device processor are loaded from either a local media, such as a diskette drive attached to the device, or from a remote host system, such as a large central processor, into a writeable random access memory (RAM) within the remote device. These RAM storage devices are generally affected by environmental conditions and have a higher failure rate than the ROS type of storage devices. Temporary or permanent device failures may occur more frequently due to bits being altered in the instruction storage by storage device failure or external environmental conditions. In prior art systems, this normally would result in the processor being halted and an indicator being set to inform the operator of the failure, resulting in loss of utilization of the device, loss of information being processed at the time of failure, and loss of operator time in reloading and restarting the device. When the device was remotely attached to a central host system, there was no automatic record made in the host system of the failure because, with an instruction error, the remote device's processor was stopped and communications with the host system was lost. This made the maintenance and problem isolation procedures for these remote devices very difficult since no record of instruction storage failure was sent to the host system.